Questions tagged [java]
Programming language and runtime environment that allows compiled Java programs to run unchanged on most hardware and software platforms
1,845
questions
146
votes
3
answers
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How can I upgrade to Java 1.8 on an Amazon Linux Server?
I tried sudo yum update but it just keeps java "1.7.0_75". I need 1.8 for it to work with another application but can't figure out how to upgrade it.
Do I need to manually install it somehow? There's ...
- 1,463
106
votes
3
answers
453k
views
What is .crt and .key files and how to generate them?
I've the following configuration:
SSLEngine on
SSLCertificateFile /etc/httpd/conf/login.domain.com.crt
SSLCertificateKeyFile /etc/httpd/conf/login.domain.com.key
SSLCipherSuite ALL:-ADH:+HIGH:+MEDIUM:...
- 1,793
105
votes
8
answers
157k
views
How to determine JAVA_HOME on Debian/Ubuntu?
On Ubuntu it is possible to have multiple JVMs at the same time. The default one is selected with update-alternatives. But this does not set the JAVA_HOME environment variable, due to a debian policy.
...
- 1,422
85
votes
5
answers
178k
views
Practical maximum open file descriptors (ulimit -n) for a high volume system
We recently began load testing our application and noticed that it ran out of file descriptors after about 24 hours.
We are running RHEL 5 on a Dell 1955:
CPU: 2 x Dual Core 2.66GHz 4MB 5150 / ...
- 953
77
votes
9
answers
202k
views
Can't seem to disable Java Automatic Update
I'm just tweaking out my new Windows 7 laptop and wanted to disable the automatic Java updating (and thus kill the silly jusched.exe background process), but I can't seem to get it to actually turn it ...
- 1,811
45
votes
5
answers
11k
views
How do I install the JRE on a Windows server without Oracle adware?
I would like to install Java on one of our servers, but I am reticent due to Oracle's bundling of an Ask.com toolbar and some virus scanner. I've read that the java updater even installs these for ...
- 661
44
votes
8
answers
225k
views
What is the value of JAVA_HOME for CentOS?
I have install java through yum on CentOS, however another java programme needs to know what the JAVA_HOME environmental variable is. I know all about setting environmental variables, but what do I ...
- 32.3k
36
votes
4
answers
144k
views
Where to set java heap options (e.g. -Xmx) for Tomcat 6 under Ubuntu 9.04?
I'm running Tomcat using the tomcat6 package from Ubuntu 9.04, which makes a daemon out of Tomcat using jsvc. I'd like to know the proper way to set Java heap options like -Xmx for Tomcat. I'd like to ...
- 1,073
33
votes
2
answers
63k
views
The option to "Launch slave agents via Java Web Start" is missing from new node configuration, how can I add it to the options menu?
I'm following this official Jenkins guide in order to become familiar with the Jenkins Pipeline configuration.
One of the steps there is to create a dumb slave and set it to "Launch slave agents via ...
- 10.8k
31
votes
8
answers
18k
views
Is it a Best Industry practice to restart web servers periodically? [closed]
We have a web application (developed by a third party) that runs on Tomcat. We have been getting very bad performance from the application. The application developer is claiming that it is an ...
- 3,081
30
votes
4
answers
69k
views
Cannot install openjdk-8-jre-headless on Debian Jessie
This Friday I saw that I had 2 held back packages for some reason when I ran apt-get upgrade, so naturally I did what any inexperienced sysadmin would do and uninstalled the packages in the hopes that ...
- 532
24
votes
5
answers
219k
views
How to get a linux network log?
We have a java server running in linux at a specific port that accepts persistent connections for thousands and thousands of users. Recently our clients are not able to connect with a time out error. ...
- 2,163
23
votes
5
answers
20k
views
I'm designing a system to handle 10000 TCP connections per second, what problems will I run into?
I have a relatively new 8-core box running CentOS. I would like to develop a stats server that uses TCP. It's very simple, it accepts a TCP connection, increments a counter and closes the connection. ...
Larry G
22
votes
6
answers
33k
views
What consumes memory in java process?
we are trying to investigate memory usage of java process under moderate load.
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
12663 test 20 0 8378m 6.0g 4492 S 43 8.4 ...
- 326
20
votes
5
answers
7k
views
What is better for a Java Web Application: more CPU cores or a higher clock speed?
I'm not sure whether serverfault is the right place to ask this, but I wonder what choice you would make if you had to select a new CPU type for your Java Web Application:
a) a CPU with 32 cores and ...
- 399
20
votes
4
answers
17k
views
Linux `alternatives --config` without user input
I am writing a RHEL kickstart script, and in my %post, I need to install a JRE.
Basically, the current setup involves me needing to manually go in after first boot and set the newly installed JRE as ...
- 392
19
votes
8
answers
140k
views
How to change default /tmp to /home/user/tmp
Is there an environment variable to set the temporary directory on debian based systems?
I have a java applet that uses that environement variable and it's getting confused when launching two ...
- 1,451
17
votes
2
answers
41k
views
Adding lines to /etc/profile with puppet?
I use puppet to install a current JDK and tomcat.
package {
[ "openjdk-6-jdk", "openjdk-6-doc", "openjdk-6-jre",
"tomcat6", "tomcat6-admin", "tomcat6-common", "tomcat6-docs",
"...
- 445
16
votes
3
answers
41k
views
Unable to change vm.max_map_count for elasticsearch
Prehistory
I have elasticsearch and SugarCRM7 running on CentOS 6.5. Every day I face the same problem: java outOfMemory error. That happens because of small vm.max_map_count value, 65530 only when ...
- 161
16
votes
3
answers
20k
views
How do you manage Java in your Windows/Active Directory environment?
Like I suppose a lot of people, we have a Windows/Active Directory environment and a lot of internal line of business apps that require Java. Our experience is that Java does not play nice in such a ...
15
votes
1
answer
38k
views
Copy a Java keystore on one machine to another?
I have a keystore on one machine (at /root/.keystore) and I want to move it to another machine at the same location. Currently, the second machine doesn't have a keystore at /root/.keystore, is there ...
- 257
15
votes
4
answers
66k
views
Cannot switch, ssh to specific user: su: cannot set user id: Resource temporarily unavailable?
/var/log/secure:
su: pam_keyinit(su-l:session): Unable to change UID to 500 temporarily
su: pam_keyinit(su-l:session): Unable to change UID to 500 temporarily
su: pam_unix(su-l:session): session ...
- 51.8k
14
votes
7
answers
101k
views
Run Jar in Background on Linux
I have a jar that runs forever (infinite loop with socket listening thread) and need it to run in the background at all times. An example would be: "java -jar test.jar" How do I do this? Thanks in ...
- 381
14
votes
2
answers
49k
views
Installing openjdk 11 on alpine:3.9
I'm trying to build an alpine docker image with openjdk 11. To do so, I'm starting an alpine container:
docker run -it alpine:3.9 /bin/sh
And running the following:
export JAVA_HOME=/opt/openjdk-11
...
- 287
13
votes
5
answers
37k
views
Set JDK 8 as the default Java on Debian 8
I'm trying to set the Java SDK 8 tools (installed from the debian backports repo) as the defaults.
# update-java-alternatives --list
java-1.7.0-openjdk-amd64 1071 /usr/lib/jvm/java-1.7.0-openjdk-...
- 973
13
votes
4
answers
534
views
How to convince my Administrator that Java ON A SERVER is not insecure per se?
The Application
We have a small Java application which uses some Camel routes to pick up uploaded files from a webserver, process them and send out some e-mails with the results.
The server on which ...
- 771
13
votes
4
answers
8k
views
ps aux hanging on high cpu/IO with java processes
I'm having some issues with java process and nrpe checks. We have some processes that sometimes use 1000% cpu on a 32 core system. The system is pretty responsive until you do a
ps aux
or try to do ...
- 22.5k
13
votes
6
answers
20k
views
Open source tomcat log viewer
I'm managing several tomcat instances (aprox 30-35) and looking for some console to centralize the logs.
I tried php-syslog-ng before (no with tomcat), and found it useful. I would like that these ...
Ari
13
votes
1
answer
62k
views
Suddenly error='Cannot allocate memory' (errno=12) [closed]
So this morning I noticed my website is down, went on my server and saw that the webserver has been stopped.
When I try to start it again I get this error
start -Dhttp.port=80 -Dapplication.secret=*...
- 245
12
votes
5
answers
25k
views
What is the difference between java.exe and javaw.exe?
On a Windows Server, I have 2 kinds of Java processes
java.exe
javaw.exe
What are the differences ?
- 2,394
12
votes
3
answers
45k
views
How to generate new, 2048-bit Diffie-Hellman parameters with Java keytool?
We are non-experts trying - unsuccessfully so far - to update our web server (JBoss-5.1.0.GA) settings to meet Diffie-Hellman standards. After running a test on https://weakdh.org/sysadmin.html, we ...
- 145
12
votes
3
answers
35k
views
SSL Certificate Error: certificate_unknown
I want to create push notification server and while installing SSL certificate and .p12 file in server we are facing the below error: I want to know what is the wrong with ssl certificate because I am ...
- 394
12
votes
4
answers
71k
views
Java error Unsigned application requesting unrestricted access to system
I want to reboot a server, so I opened its Integreted Dell Remote Access Controller in Chrome, and clicked on "start virtual console", which caused Chrome to download a file with a strange name. The ...
- 121
12
votes
2
answers
16k
views
Disabling SSLv3 but still supporting SSLv2Hello in Apache
Many SSL clients, notably JDK 6, use the SSLv2Hello protocol to handshake with the server.
Using this protocol does not mean you are using SSL 2.0 or 3.0 for that matter; it is merely
a handshake to ...
- 231
11
votes
7
answers
33k
views
How to block access to a file from being served by Tomcat?
We have a few tomcat servers and we just discovered that some files that we don't want public to have access to those files. To exemplify:
Let say we have a folder /var/www/html/ that we are ...
- 3,081
11
votes
4
answers
44k
views
Which Java version should I run Jenkins with?
Reference: Jenkins Users :: Jenkins on Windows: Java + JRE (version) confusion
Which Java version should I run Jenkins with (on Windows)? Should I use the included JRE of the Windows master? Should ...
- 599
11
votes
8
answers
48k
views
Batch file to uninstall all Sun Java versions?
I'm setting up a system to keep Java in our office up to date. Everyone has all different versions of Java, many of them old and insecure, and some dating back as far as 1.4. I have a System Center ...
- 439
11
votes
1
answer
9k
views
Is it appropriate to use HeapDumpOnOutOfMemoryError in Production?
We have been struggling to diagnose the cause of an OutOfMemoryError we experienced on one of our production servers. Our attempts to reproduce the issue in soak tests have so far failed, and we are ...
- 223
10
votes
4
answers
6k
views
is it possible to install java without the browser plugin?
I need java, but I don't want any browser to be able to access it.
Is it possible to remove the whole applet/browser plugin code?
- 345
10
votes
4
answers
50k
views
Why isn't there a openjdk-8-jdk package on debian anymore?
On a docker container running the latest debian image I'm unable to install the openjdk-8-jdk package. Why not suddenly?
$ apt-get install openjdk-8-jdk
E: Unable to locate package openjdk-8-jdk
Why ...
- 159
10
votes
4
answers
25k
views
Constantly Increasing swap size in Linux and Swap space not being reclaimed?
I have a 8GB RAM linux box on which 4 tomcat servers are running. One of the them is set to 3000MB memory(jvm -Xms and -Xmx setting) and others are set to 1500MB. The swap partition is also set to ...
- 281
10
votes
6
answers
83k
views
Supermicro IPMIView KVM Console does not work at all
I can't get the Supermicro IPMIView version 2.* (any of them) to launch the KVM Console either in the IPMIView windows program nor any browser. Java, is installed (version 8, update 131) and I'm ...
- 301
10
votes
1
answer
19k
views
How can I restrict the java plugin to run only on certain sites in Internet Explorer?
I want to secure our centrally managed computers better and it is very difficult to automatically deploy the java runtime, but how to do that is another question.
I find the security of Java ...
- 1,052
10
votes
1
answer
85k
views
Differences between classes12.jar, ojdbc14.jar, ojdbc5.jar and ojdbc6.jar
We are planning to upgrade our application servers to a new version of JRun which is carrying with it an upgrade from Java 1.4 to Java 1.6. As part of that, we have been testing various pieces of our ...
- 3,234
9
votes
2
answers
2k
views
How do you get the latest update for Java 6?
An application my company is considering buying requires Java 6. I am concerned that this is quite out of date and am recommending against the application as a result. But it seems that Oracle do ...
- 685
9
votes
5
answers
4k
views
How do I find the cause for a huge difference in performance between two identical Ubuntu servers?
I am running two Dell R410 servers in the same rack of a data center (behind a load balancer). Both have the same hardware configuration, run Ubuntu 10.4, have the same packages installed and run the ...
- 93
9
votes
5
answers
18k
views
How to reliably take Java Heap Dumps?
My team is running into difficulties when trying to take good heap dumps triggered by OutOfMemoryErrors. For specific reasons we are currently taking the dumps with jmap called from a bash script ...
- 153
9
votes
5
answers
19k
views
Tomcat 6.0 service does not start: java/lang/NoClassDefFoundError
I installed Tomcat on my Windows server but I can't get it to start. I start the service and I see the progress bar, but it fails.
I installed the Java Runtime Environment Version 6 and created ...
- 627
9
votes
3
answers
26k
views
Load Balancer on Amazon does not have secure flag set for Cookie
We have a java based application running on Amazon and have configured our Amazon ELB to connect to them successfully.
However, we are seeing that the Cookie flag not set as Secure.
Name Value ...
- 485
9
votes
3
answers
19k
views
Jenkins CI - Cannot allocate memory
I tested jenkins-ci successfully on a ubuntu 10.4 (with vmware fusion) on my local computer. Now I want to install and use it on my virtual server at hosteurope. The basic installation was no problem, ...
- 91